Feb. 28--A change Congressional Republicans made to one part of the Affordable Care Act means that courts should overturn the entire law, according to a lawsuit that Kansas and Missouri signed onto this week.

Kansas Attorney General Derek Schmidt and Missouri Attorney General Josh Hawley joined officials in 18 other Republican-led states in the latest challenge to the law commonly called Obamacare.

Most of the 2010 law's sweeping health insurance changes have survived previous lawsuits and Republican promises of complete repeal through the legislative process. This year's repeal efforts in Congress, energized by President Donald Trump's election, mostly fizzled. But they produced one significant change: the end of the tax penalty for individual Americans who don't carry health insurance, effective in 2019.

While the tax was repealed, the mandate to carry insurance is still a part of the law, if only symbolically. Schmidt said that, plus an earlier U.S. Supreme Court decision on the issue, means the ACA should now be ruled unconstitutional.

"In 2012, the Supreme Court left the Obamacare mandate hanging by the thinnest of legal threads," Schmidt said. "We think Congress snipped that thread in the tax reform bill."

Wisconsin Attorney General Brad Schimel and Texas Attorney General Ken Paxton filed the complaint Monday in a federal court in Texas.

If the court rules that the individual mandate is now unconstitutional, it could allow the rest of the law to stand. But the "severability" of that mandate was a point of contention among the Supreme Court justices in 2012, with four of them arguing that the entire law should stand or fall together.

In addition to Kansas and Missouri, the other states participating are Alabama, Arizona, Arkansas, Florida, Georgia, Indiana, Louisiana, Maine, Mississippi, Nebraska, North Dakota, South Carolina, South Dakota, Tennessee, Utah and West Virginia.

A nonprofit called the Protect our Care Campaign, formed to oppose Obamacare repeal efforts, blasted the lawsuit Tuesday as a "partisan attack." The group said it puts at risk popular provisions of the ACA like guaranteed access to coverage for people with pre-existing conditions and allowing children to stay insured under their parents' plans until age 26.

"It's time for Derek Schmidt and President Trump to move on from their war on Kansans' health care and start working on bipartisan solutions to protect people's coverage and bring costs down," said Protect Our Care Campaign director Brad Woodhouse.